This invention relates to a method of manufacturing a bolometer-type non-cooling infrared sensor that changes the temperature of a light-incident portion thereof by absorption of incident infrared light so as to change the electrical resistance value of a resistor by the temperature change, thereby outputting a signal indicative of the infrared radiation intensity.
A bolometer utilizes the temperature variation of electrical resistance of a metal or semiconductor thin film that is thermally insulated from a substrate material. Generally, as a temperature coefficient of resistance (hereinafter referred to as a “TCR”) of the bolometer material, i.e. the material of the metal or semiconductor thin film, increases, the detection sensitivity is improved and a noise equivalent temperature difference (hereinafter referred to as an “NETD”) representing the temperature resolution of the infrared sensor decreases.
An alloy thin film such as a nickel-iron alloy thin film has a small TCR of about 0.5%/K. Therefore, it is considered that a conductive oxide thin film such as a vanadium oxide thin film, a perovskite-type Mn oxide thin film, or a YBa2Cu3Ox thin film is preferable as a bolometer resistor film for use in a highly sensitive infrared sensor.
A manufacturing method of an infrared sensor having such a conductive oxide thin film is described, for example, in Patent Document 1 (Japanese Unexamined Patent Application Publication (JP-A) No. 2002-289931).
In the manufacturing method according to Patent Document 1, a bridge structure formed on an Si substrate via a gap, a bolometer resistor film formed on the bridge structure, and a protective layer formed on the surface of the bridge structure including the bolometer resistor film are each formed as an oxide thin film by dissolving a metal-organic compound in a solvent to make a solution, then coating and drying it, and then irradiating it with laser light having a wavelength of 400 nm or less to thereby cut and decompose carbon-oxygen bonds.
It has been confirmed that, according to this manufacturing method, the bolometer resistor film having a predetermined sheet resistance and TCR is obtained by laser annealing for several minutes as compared with a heat treatment method which requires thermal annealing for several hours to several tens of hours.
In the manufacturing method as described above, although an effect is obtained that the number of processes can be reduced by forming the bridge structure, the bolometer resistor film, and the protective layer, respectively, by the coating method, there is a problem that the coating method is not suitable for mass production.
Further, there is room for improvement in TCR with respect to the bolometer resistor film made of vanadium oxide.